Power sharing coordination of paralleled sources

ABSTRACT

Systems for power sharing coordination of parallel sources are provided. Aspects include a first DC power supply, a second DC power supply, a first generator controller configured to operate the first DC power source, a first current sensing device coupled between the first DC power supply and the common bus point, a second current sensing device coupled between the common bus point and a load, wherein the first generator controller is configured to receive a first current signal from the first current sensing device, receive a second current signal from the second current sensing device, determine a load share percentage for the first DC power supply, determine a first voltage adjustment based on the first current signal, the second current signal, and the load share percentage, and operate the first DC power supply to adjust a first voltage output by the first voltage adjustment.

BACKGROUND

The present invention generally relates to parallel direct current (DC)sources, and more specifically, to power sharing coordination ofparalleled sources.

Aircraft require electrical power to operate many parts of the aircraftsystem, including on-board flight control systems, lighting, airconditioning etc. The current and future generations of aircraft usemore and more electrical control in place of conventional hydraulic,pneumatic etc. control. Such more electric aircraft (MEA) haveadvantages in terms of the size and weight of the controls and powersystems as well as in terms of maintenance and reliability.

Most current large commercial aircraft use electricity, on-board, in theform of an AC fixed frequency and/or variable frequency network. Stepshave been made to move from 115 V ac to 230 V ac and more recentdevelopments have allowed power supplies to supply high voltage dc(HVDC) e.g. +/−270 V dc, providing improvements in terms of additionalfunctionality, power supply simplification, weight savings and thus fuelefficiency.

Generally, voltage is provided on board an aircraft in one of two (ormore) ways. When the aircraft is on the ground, power comes from anexternal ground generator supplying, say 115 V ac at 400 Hz. Anauto-transformer rectifier unit (ATRU) rectifies the supply voltage toprovide voltages required for the different loads on the aircraft.Instead of an ATRU, the power can be rectified by active rectificationusing power flow controllers.

When the aircraft is in the air the power comes from the aircraft engineor auxiliary power unit (APU) via a three-phase ac generator that couldthen be rectified. The rectified power is provided to a so-called DCbus.

BRIEF DESCRIPTION

Embodiments of the present invention are directed to a system. Anon-limiting example of the system includes a first direct current (DC)power supply including a first generator and a first rectifier circuit,a second DC power supply, wherein a first output of the first DC powersupply and a second output of the second DC power supply are commonlycoupled at a common bus point, a first generator controller configuredto operate the first DC power source, a first current sensing devicecoupled between the first output of the first DC power supply and thecommon bus point, a second current sensing device coupled between thecommon bus point and a load, wherein the first generator controller isconfigured to receive a first current signal from the first currentsensing device, receive a second current signal from the second currentsensing device, determine a load share percentage for the first DC powersupply, determine a first voltage adjustment value based on the firstcurrent signal, the second current signal, and the load sharepercentage, and operate the first DC power supply to adjust a firstvoltage output of the first DC power supply by the first voltageadjustment value.

Embodiments of the present invention are directed to a system. Anon-limiting example of the system includes a first direct current (DC)power supply including a first generator and a first rectifier circuit,a second DC power supply, wherein a first output of the first DC powersupply and a second output of the second DC power supply are commonlycoupled at a common bus point, a first generator controller configuredto operate the first DC power source, a first current sensing devicecoupled between the first output of the first DC power supply and thecommon bus point, a second current sensing device coupled between thecommon bus point and a load, a supervisory controller communicativelycoupled to the first generator controller, wherein the supervisorycontroller is configured to receive a first current signal from thefirst current sensing device, receive a second current signal from thesecond current sensing device, determine a first voltage adjustmentvalue for the first DC power supply based on the first current signaland the second current signal, and command the first generatorcontroller to operate the first DC power supply to adjust a firstvoltage output of the first DC power supply by the first voltageadjustment value.

Additional technical features and benefits are realized through thetechniques of the present invention. Embodiments and aspects of theinvention are described in detail herein and are considered a part ofthe claimed subject matter. For a better understanding, refer to thedetailed description and to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The specifics of the exclusive rights described herein are particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The foregoing and other features and advantages ofthe embodiments of the invention are apparent from the followingdetailed description taken in conjunction with the accompanying drawingsin which:

FIG. 1 is a perspective view of an aircraft that may incorporateembodiments of the present disclosure;

FIG. 2 depicts a block diagram of a system utilizing a supervisorycontroller for active power regulation of parallel DC sources accordingto one or more embodiments; and

FIG. 3 depicts a block diagram of a system utilizing a supervisorycontroller for passive power regulation of parallel DC sources accordingto one or more embodiments.

The diagrams depicted herein are illustrative. There can be manyvariations to the diagram or the operations described therein withoutdeparting from the spirit of the invention. For instance, the actionscan be performed in a differing order or actions can be added, deletedor modified. Also, the term “coupled” and variations thereof describeshaving a communications path between two elements and does not imply adirect connection between the elements with no interveningelements/connections between them. All of these variations areconsidered a part of the specification.

DETAILED DESCRIPTION

For the sake of brevity, conventional techniques related to making andusing aspects of the invention may or may not be described in detailherein. In particular, various aspects of aircraft electric powersystems to implement the various technical features described herein arewell known. Accordingly, in the interest of brevity, many conventionalimplementation details are only mentioned briefly herein or are omittedentirely without providing the well-known system and/or process details.

FIG. 1 illustrates an example of a commercial aircraft 10 havingaircraft engines 20 that may embody aspects of the teachings of thisdisclosure. The aircraft 10 includes two wings 22 that each include oneor more slats 24 and one or more flaps 26. The aircraft further includesailerons 27, spoilers 28, horizontal stabilizer trim tabs 29, rudder 30and horizontal stabilizer 31. The term “control surface” used hereinincludes but is not limited to either a slat or a flap or any of theabove described. It will be understood that the slats 24 and/or theflaps 26 can include one or more slat/flap panels that move together.The aircraft 10 also includes a system 200 (described in greater detailin FIG. 2) which allows for power sharing coordination for parallelsources according to one or more embodiments. The parallel sources cansupply power to a DC bus that provides power for a variety of powerapplications on the aircraft.

Turning now to an overview of technologies that are more specificallyrelevant to aspects of the disclosure, when the aircraft is in the airthe power comes from an electric power generating system (EPGS) whichtypically includes one or more generators. An example generatorincludes, but it not limited to, permanent magnet generators (PMG) thatinclude permanent magnets mounted on a rotating shaft driven by a primemover such as the turbine engine on the aircraft. The power generatorfrom these generators can be rectified to provide a DC power supply topower a DC bus on the aircraft. In some instances, it may be desirableto have two (or more) DC power supplies operating in parallel to provideDC power to the DC bus. This allows for the DC power bus to provide morepower for large loads such as an electrical propulsion system.

Using parallel DC power supplies provide flexibility when there is ademand for a high load current that is more than a single DC powersupply can provide. Advantages of the parallel supplies versus using alarger DC power supply includes the ability for independent channeloperation, installation flexibility & the load management configuration.

However, two or more DC power supplies connected in parallel do notautomatically share a load equally. Even if the power supplies areidentical, the output voltages will be slightly different due tocomponent tolerances and a variety of other factors. The power supplywith the higher output will typically provide the entire load current,operating at its limit while the other power supply essentially doesvery little work. This scenario is not optimal because it essentiallyoverloads a power supply which could cause the power supply to fail at afaster rate.

In one or more embodiments, aspects described herein address powersharing amongst parallel DC power supplies by providing a power sharingcoordination system and associated methodology for operation. Asupervisory controller is utilized to coordinate power sharing amongparalleled DC power sources. When two sources are paralleled, the amountof power drawn from each source depends on the characteristics of thegenerator controllers. Aspects herein include the introduction of asupervisory controller that interacts with the individual generatorcontrollers to either adjust the generator controller's command or theirgain to achieve a desired power sharing amongst the parallel DC sources.

In one or more embodiments, the supervisory power controller can beimplemented in both an actively power regulated paralleling scheme and apassively regulated paralleling scheme. In an active power regulatedparalleling scheme, each individual generator controller takes intoaccount the entire load on the system (i.e., the summed load of theother DC power sources) when regulating the load sharing portion of thesystem load. In a passive power regulated paralleling scheme, eachindividual generator controller only takes into account the loadinformation of the individual power source when regulating the generatorpower.

FIG. 2 depicts a block diagram of a system utilizing a supervisorycontroller for active power regulation of parallel DC sources accordingto one or more embodiments. The system 200 includes two generators 206a, 206 b that are arranged in parallel. While the illustrated exampleshows only two generators 206 a, 206 b, any number of parallel powersources can be utilized in one or more embodiments. The generators 206can be wound field synchronous generators on an aircraft for example.The system 200 also includes a two rectifiers 208 a, 208 b which can beany type of rectifier circuit including, but not limited to, active andpassive rectifiers. The rectifiers 208 a, 208 b convert the AC powerfrom the generators 206 a, 206 b to DC power. In one or moreembodiments, the DC power voltage is a high voltage DC (HVDC). Thesystem 200 includes an impedance 210 a, 210 b to capture parasiticimpedance of the feeders. In general, the bus includes feeder impedances(e.g. resistance and inductance between the generator and rectifier, aspart of the rectifier/filter circuit, between the rectifier and point ofcommon coupling (PCC), and between the PCC and the load. As shown in thesystem 200, the DC bus is commonly coupled to provide DC power to theload 220 at a point of common coupling 214. The DC bus can have a filter218 attached between the point of common coupling 214 and the load 220on the system 200. In some embodiments, the filter 218 can be positionedbefore the point of common coupling 214 of the DC bus, for example twofilters could be directly after the two rectifiers 206 a, 206 b. Thefilter 218 can be any type of electronic filter.

In one or more embodiments, the generators 206 a, 206 b are controlledand operated by a generator controller 202 a, 202 b. Further, thegenerator controllers 202 a, 202 b are configured to receive currentreadings and/or signals from a first and second current sensing device212 a, 212 b located between the respective generators 206 a, 206 b thepoint of common coupling 214 of the DC bus. In addition, the generatorcontrollers 202 a, 202 b can receive current readings and/or signalsfrom a third current sensing device 216 between the point of commoncoupling 214 of the DC bus and the load 220. The current sensing devices212 a, 212 b, 216 can be any type of device operable to sense currentvalues from a bus such as, for example, a hall effect sensor or acurrent sense resistor. In one or more embodiments, the individualcurrents Idc0, Idc1 can be routed to each generator controller 202 a,202 b and internally summed to arrive at the total load current.

In one or more embodiments, the system 200 includes a supervisorycontroller 204. The supervisory controller 204 is configured to providea load power percentage command to the generator controllers 202 a, 202b which designates the percentage of the overall load power requiredfrom each generator 206 a, 206 b. The generator controllers 202 a, 202 bregulate the DC power to achieve the desired load share for each source.In one or more embodiments, the supervisory controller 204 can determinethe appropriate load sharing command to provide based on aircraftoperating conditions and one or more performance goals. For example, ifthe two generators 206 a, 206 b are connected to the low and high-spoolsof the engine respectively, the load sharing could be adjusted tominimize fuel burn. Another example includes a scenario where one of thegenerators is a battery source paralleled with a rectified generator. Inthis scenario, the load share could be a constant command so that the DCpower tracks the state of charge of the battery as it discharges. Thatis to say, the generators 206 a, 206 b could be a battery source as wellas an AC generator power source and/or any combination of power sources.

In one or more embodiments, the supervisory controller 204 provides thepercentage load share for each generator controller 202 a, 202 b. Thegenerator controllers 202 a, 202 b can receive current signals and/orcurrent values from the first and second current sensing devices 212 a,212 b as well as the third current sensing device 216. The third currentsensing device 216 provides a current signal and/or current value forthe overall current provided to the load after the point of commoncoupling 216. The first current sensing device 212 a provides thecurrent signal and/or value for the first power source and the secondcurrent sensing device 212 b provides the current signal and/or currentvalue for the second power source. The two generator controllers 202 a,202 b uses the current signals and/or values to determine theappropriate command to regulate the power of the respective generators206 a, 206 b to share the total load on the system at the percentageprovided by the supervisory controller. In some embodiments, thesupervisory controllers 204 can receive instructions from an exteriorsource (such as the pilot) as to the percentage of load share for thegenerators and/or power sources (in the case of a battery).

In one or more embodiments, the generator controllers 202 a, 202 b areconfigured to reduce or “droop” the voltage output of the generators 206a, 206 b in the system 200 responsive to sensing a feedback currentmeasured from the current sensing devices 212 a, 212 b and the totalcurrent on the load 220 measured from the third current sensing device216. The generator controllers 202 a, 202 b adjust the droop of theirrespective generators 206 a, 206 b using the respective percentagecommand received from the supervisory controller 204. This could beimplemented as an outer loop feedback regulator on the % Current (orPower), adjusting the voltage command to actively regulate powersharing. This could either boost and/or droop the voltage set-point,with appropriate limits as to how far the set-point can be adjustedgiven the system architecture and requirements.

FIG. 3 depicts a block diagram of a system utilizing a supervisorycontroller for passive power regulation of parallel DC sources accordingto one or more embodiments. The system 300 includes two generators 306a, 306 b that are arranged in parallel. The generators 306 can be woundfiled synchronous generators on an aircraft as discussed above. Thesystem 300 also includes a two rectifiers 308 a, 308 b which can be anytype of rectifier circuit including both active and passive rectifiers.The rectifiers 308 a, 308 b convert the AC power from the generators 306a, 306 b to DC power. In one or more embodiments, the DC power voltageis a high voltage DC (HVDC). The system 300 includes an impedance 310 a,310 b to capture parasitic impedance of the feeders. In general, the busincludes feeder impedances (e.g. resistance and inductance between thegenerator and rectifier, as part of the rectifier/filter circuit,between the rectifier and point of common coupling (PCC), and betweenthe PCC and the load. As shown in the system 300, the DC bus is commonlycoupled to provide DC power to the load 320 at a point of commoncoupling 314. The DC bus can have a filter 318 attached between thepoint of common coupling 314 and the load 320 on the system 300. In someembodiments, the filter 318 can be positioned before the point of commoncoupling 314 of the DC bus, for example two filters could be directlyafter the two rectifiers 308 a, 308 b. The filter 318 can be any type ofelectronic filter.

In one or more embodiments, the generators 306 a, 306 b are controlledand operated by a generator controller 302 a, 302 b. Further, thegenerator controllers 302 a, 302 b are configured to receive currentreadings and/or signals from a first and second current sensing device312 a, 312 b located between the respective generators 306 a, 306 b thepoint of common coupling 314 of the DC bus. The current sensing devices312 a, 312 b can be any type of device operable to sense current valuesfrom a bus such as, for example, a hall effect sensor or a current senseresistor

In one or more embodiments, the system 300 includes a supervisorycontroller 304 which is configured to receive a current signal and/orvalue from the first and second current sensing devices 312 a, 312 b aswell as a current signal and/or value from a third current sendingdevice 306 located after the point of common coupling 314 of the DC bus.The supervisory controller 304 analyzes the current signals and/orvalues to determine a voltage adjustment for the generator controllers302 a, 302 b. The voltage adjustment can droop and/or boost the voltageoutput. In one or more embodiments, the voltage adjustment can be donein at least three ways including (1) boosting a voltage on the firstgenerator 306 a and drooping a voltage on the second generator 306 b;(2) boosting a voltage on the first generator 306 a and leaving thesecond generator 306 b unchanged; and (3) drooping the voltage on thefirst generator 306 a and leaving the second generator 306 b unchanged.Droop refers to the reduction of the voltage output of the generators306 a, 306 b for load sharing. Increasing the voltage can be a gaincalculation passed on to the generator controllers 302 a, 302 b Thecalculation of the droop/increase gain is performed at the supervisorycontroller 304 and passed to the generator controllers 302 a, 302 b toreduce or increase the voltage accordingly. In one or more embodiments,the supervisory controller 304 can determine the voltage adjustmentvalue and/or gain command to provide based on aircraft operatingconditions and one or more performance goals for the aircraft.

In one or more embodiments, the generator controllers 202 a, 202 b, 302a, 302 b and/or supervisory controller 204, 304 can receive DC currentvalues from the current sensing devices 212 a, 212 b, 216, 312 a, 312 b,316 at a defined sampling rate. An exemplary sampling rate could bebetween 50-100 μs. Any sampling rate can be utilized herein.

In one or more embodiments, the generator controllers 202 a, 202 b, 302a, 302 b and supervisory controllers 204, 304 or any of the hardwarereferenced in the systems 200, 300 can be implemented by executableinstructions and/or circuitry such as a processing circuit and memory.The processing circuit can be embodied in any type of central processingunit (CPU), including a microprocessor, a digital signal processor(DSP), a microcontroller, an application specific integrated circuit(ASIC), a field programmable gate array (FPGA), or the like. Also, inembodiments, the memory may include random access memory (RAM), readonly memory (ROM), or other electronic, optical, magnetic, or any othercomputer readable medium onto which is stored data and algorithms asexecutable instructions in a non-transitory form.

The term “about” is intended to include the degree of error associatedwith measurement of the particular quantity based upon the equipmentavailable at the time of filing the application. For example, “about”can include a range of ±8% or 5%, or 2% of a given value.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the presentdisclosure. As used herein, the singular forms “a”, “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises” and/or “comprising,” when used in this specification,specify the presence of stated features, integers, steps, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,element components, and/or groups thereof.

Various embodiments of the invention are described herein with referenceto the related drawings. Alternative embodiments of the invention can bedevised without departing from the scope of this invention. Variousconnections and positional relationships (e.g., over, below, adjacent,etc.) are set forth between elements in the following description and inthe drawings. These connections and/or positional relationships, unlessspecified otherwise, can be direct or indirect, and the presentinvention is not intended to be limiting in this respect. Accordingly, acoupling of entities can refer to either a direct or an indirectcoupling, and a positional relationship between entities can be a director indirect positional relationship. Moreover, the various tasks andprocess steps described herein can be incorporated into a morecomprehensive procedure or process having additional steps orfunctionality not described in detail herein.

The following definitions and abbreviations are to be used for theinterpretation of the claims and the specification. As used herein, theterms “comprises,” “comprising,” “includes,” “including,” “has,”“having,” “contains” or “containing,” or any other variation thereof,are intended to cover a non-exclusive inclusion. For example, acomposition, a mixture, process, method, article, or apparatus thatcomprises a list of elements is not necessarily limited to only thoseelements but can include other elements not expressly listed or inherentto such composition, mixture, process, method, article, or apparatus.

Additionally, the term “exemplary” is used herein to mean “serving as anexample, instance or illustration.” Any embodiment or design describedherein as “exemplary” is not necessarily to be construed as preferred oradvantageous over other embodiments or designs. The terms “at least one”and “one or more” may be understood to include any integer numbergreater than or equal to one, i.e. one, two, three, four, etc. The terms“a plurality” may be understood to include any integer number greaterthan or equal to two, i.e. two, three, four, five, etc. The term“connection” may include both an indirect “connection” and a direct“connection.”

While the present disclosure has been described with reference to anexemplary embodiment or embodiments, it will be understood by thoseskilled in the art that various changes may be made and equivalents maybe substituted for elements thereof without departing from the scope ofthe present disclosure. In addition, many modifications may be made toadapt a particular situation or material to the teachings of the presentdisclosure without departing from the essential scope thereof.Therefore, it is intended that the present disclosure not be limited tothe particular embodiment disclosed as the best mode contemplated forcarrying out this present disclosure, but that the present disclosurewill include all embodiments falling within the scope of the claims.

What is claimed is:
 1. A system comprising: a first direct current (DC)power supply comprising a first generator and a first rectifier circuit;a second DC power supply, wherein a first output of the first DC powersupply and a second output of the second DC power supply are commonlycoupled at a common bus point; a first generator controller configuredto operate the first DC power source; a first current sensing devicecoupled between the first output of the first DC power supply and thecommon bus point; a second current sensing device coupled between thecommon bus point and a load; wherein the first generator controller isconfigured to: receive a first current signal from the first currentsensing device; receive a second current signal from the second currentsensing device; determine a load share percentage for the first DC powersupply; determine a first voltage adjustment value based on the firstcurrent signal, the second current signal, and the load sharepercentage; and operate the first DC power supply to adjust a firstvoltage output of the first DC power supply by the first voltageadjustment value.
 2. The system of claim 1, wherein the first DC powersupply is in parallel with the second DC power supply.
 3. The system ofclaim 1, further comprises: a supervisory controller communicativelycoupled to the first generator controller, wherein determining the loadshare percentage for the first DC power supply comprises receiving, fromthe supervisory controller, a command comprising the load sharepercentage.
 4. The system of claim 1, wherein the first DC power supplyis housed on an aircraft; and wherein the load share percentage isdetermined based on one or more performance goals of the aircraft. 5.The system of claim 1, further comprising: a third current sensingdevice coupled between the second output of the second DC power supplyand the common bus point; a second generator controller configured tooperate the second DC power source, wherein the second generatorcontroller is configured to: receive a third current signal from a thirdcurrent sensing device; receive the second current signal from thesecond current sensing device; determine a second load share percentagefor the second DC power supply; determine a second voltage adjustmentvalue based on the third current signal, the second current signal, andthe second load share percentage; and operate the second DC power supplyto adjust a second voltage output of the second DC power supply by thesecond voltage adjustment value.
 6. The system of claim 5, furthercomprising: a supervisory controller communicatively coupled to thesecond generator controller, wherein determining the second load sharepercentage for the second DC power supply comprises receiving, from thesupervisory controller, a command comprising the second load sharepercentage.
 7. The system of claim 5, wherein the second DC power supplycomprises a second generator and a second rectifier circuit.
 8. Thesystem of claim 1, wherein the second DC power supply comprises abattery.
 9. The system of claim 1, wherein the first current sensingdevice comprises a hall effect sensor.
 10. The system of claim 1,wherein the first generator comprises a permanent magnet generator.